How long will 3amp fridge run on 600amp battery?-gctid390333

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http://www.atozmarine.net/norcold_dc0040.htm

How long will this last on 600amp battery?

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You can calculate this yourself by finding the Amp Hour capacity (AH) of the battery in question. 1 AH equals a draw of 1 amp for 1 hour. If you have an 80 AH battery, fully charged, with no other load other than the fridge, in theory, your 80 AH battery can power your 3 amp load for 26+ hours.

In theory...

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Bob's right. We need the battery amp-hours, not amps. You do not want to draw more than about 50% of the battery's A-h rating.

And that fridge is only drawing 2.7A when it's running. It may only run 60-70% of the time when the boat is hot, and less if the boat is cool.

So assume battery A-h is 80A-h, then 80x0.5 / (2.7x0.7)= approx safe run time. Or about 21 hours.

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green650 wrote:
http://www.atozmarine.net/norcold_dc0040.htm

How long will this last on 600amp battery?

Please..no slide rule mechanics...these are rough numbers!

Assuming 600 is 600 AH and you don't want to discharge much more than 50% or 300 ah ..so.....(300/3)/duty cycle = 100 hours at a duty cycle of 100%.

The frig duty cycle (% of an hour it runs) is probably around 70% so (300ah/3amps)/.7= 143 hours to 1/2 discharge.

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lolar3288 wrote:
Please..no slide rule mechanics...these are rough numbers!

Assuming 600 is 600 AH and you don't want to discharge much more than 50% or 300 ah ..so.....(300/3)/duty cycle = 100 hours at a duty cycle of 100%.

The frig duty cycle (% of an hour it runs) is probably around 70% so (300ah/3amps)/.7= 143 hours to 1/2 discharge.

I really doubt he's got 600A-h of installed battery capacity Larry. I'm guessing that is CCA he is quoting.

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whiskywizard wrote:
I really doubt he's got 600A-h of installed battery capacity Larry. I'm guessing that is CCA he is quoting.

If your right he probably has less than 125 ah full capacity so at 1/2 that's 63ah.....Something like 20-30 hours of run time!

[captharv Founding Member Find all posts View Profile Close captharv]

Read this. Should answeryour questions

http://www.baylinerownersclub.org/fo...ad.php?t=35340

[Guest Cleaning the Bilge Find all posts View Profile Close Guest]

I have 2 of these:

http://www.atbatt.com/product/24022....tm_term=SRM-24

It looks like they are 84ah.

Im hoping to be able to run the fridge all day while out cruising, boat on probably half the time.

And also would be nice if the fridge could be left on overnight if I spend the night out on the islands. If not, Ill keep the storage space on the boat and just go with an ice chest when needed.

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definitely a 84Ah battery. Under the above assumptions of a 3A draw, 70% DC and 50% discharge you are at 20h run time. However, they usually have quite a current surge on start which could negate the 70%DC if it starts pretty often. If that's the case you may be down to 14h.

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You can increase your AH capacity by installing a Group 31 battery for your house batt. Depending on make and model you can get another 20 to 30 AH. The 31 is a bit larger than the 24 though so that's a consideration.

[Garchar Seasoned Member Find all posts View Profile Close Garchar]

I hear and see a lot of great battery charging information on this post. One important missing piece of the puzzle is the actual switching of the batteries from 1 to 2 or all. I have been told by most boat shops and old timers to NOT switch the batteries when under way. Does anyone disagree?? Gary

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it depends on the switch and the risk you are willing to take. The switches should be "make-before-break" but if a switch gets older it may still open for a few milliseconds. That's enough for the diodes in the alternator to pass away.

For me that's a reason to NEVER install a switch without AFD (alternator field disconnect). There's simply a diode from the alternator side to one (or 2 diodes to both) batteries. In case the switch goes open circuit the diode(s) will clamp the voltage to the battery voltage plus voltage drop of the diode (for these ratings typicall ~1V) which si safe for the alternator diodes. In normal mode the diode(s) is reverse biased which means it looks like they aren't there.

Side note: the crazy thing is that a single switch with AFD is more expensive than a dual battery switch with AFD (same model series for Attwood and blue-sea I checked)! More material and lower price....

[Iproff Guru Find all posts View Profile Close Iproff]

green650 wrote:
I have 2 of these:

http://www.atbatt.com/product/24022....tm_term=SRM-24

It looks like they are 84ah.

Im hoping to be able to run the fridge all day while out cruising, boat on probably half the time.

And also would be nice if the fridge could be left on overnight if I spend the night out on the islands. If not, Ill keep the storage space on the boat and just go with an ice chest when needed.

For 7 years in a row I anchored out a lot then my health stopped that for the last 2 years but here is what I have and the time between recharge. I have a Trec II fridge draws 2.5 but start up is more, these readings are off my Link 1000. I have 220 ah in my golf cart batteries. If I am on the boat and on the hook, I get 18 hrs. before my batteries drop to 110 to 115 ah. If it is at the dock and the power goes out and I don't have any thing turned on and I don't open the fridge I get about 3 days.

The outside air and water temperature have a huge impact on how often the fridge comes on in the late fall and early spring it comes on a lot less than in July and August. When you are on the hook over night you can't be sitting in the dark or not have an anchor light on. When you start to add all these things up your recharge time drops. It's not as simple as figuring out the fridge alone, my anchor light draws more ah than my fridge over night.

Ken

[BLCarl Frequent Contributor Find all posts View Profile Close BLCarl]

My 1998 Norcold DE 35D was a power hog . 12 hrs on a pair of costco cart batteries and they are in very weak condition. I understand the new Norcolds are much improved I'll soon find out because the old one died during the winter. With this in mind the 2K Yamaha generator changed my battery procedure completely Recharge time is just a few hours with a 35A charger.

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If House Bank Battery run time is of any concern to you at all, then invest in a simple Monitoring system like the Link Lite or similar product. The install is VERY easy and a perfect do it yourself project.

These systems will tell you everything you need to know about your batteries and the various draws things demand. I just installed one after 5 years, spending MANY nights on the hook or out all day with the same concerns you have and I don't know how I did it without this unit.

But, to give you some ideas on how to figure this out in your current situation, you need to monitor how often your fridg cycles on/off at a given outside temp. So a 3amp draw will only be 1.5 if it cycles on for only 30 min in an hour.

One thing I used to do was put the fridg setting on high while underway and then turn it down to 2 (out of 5) for during the day. Before I went to bed, I would always run the boat for a half hour or so with the fridg set to high and then turn it off completely overnight without opening it.

And, as Ken suggests, other things will burn much more if you don't monitor them... lights can be a killer.

oh... did I mention that I highly recommend a monitoring system?